1. Field of the Invention
The invention in general relates to line leak test probes which are used in leak detectors which monitor liquid storage and dispensing systems for leaks and more particularly to such a probe which determines if there is a leak by measuring the rate of pressure change.
2. Description of the Prior Art
Line leak test probes have been used in the petroleum industry for many years. Such line leak test probes generally report to a central monitor which utilizes the leak information to provide warning of leaks and to shut down pumps on lines that are leaking. Such probes have become an essential part of hydrocarbon storage and dispensing facilities since even very small leaks can result in the loss of thousands of dollars in hydrocarbons and the additional expenses of cleanup can be enormous. It is believed that the state of the art of such probes is described in U.S. Pat. No. 4,835,717 issued to Hilary Michel and Laurence S. Slocum which is hereby incorporated by reference. This patent discloses a line leak test probe that includes a microprocessor that is able to distinguish pressure drops that do not indicate a leak, such as those caused by a person opening the dispensing valve before the pump is turned on, which enables the probe to avoid giving false alarms in such instances. However, all of the prior art line leak probes that rely on pressure measurements, determine if there is a leak by detecting when some minumum pressure is reached. Since it is difficult to anticipate all instance in which a non-leaking system might fall below the minimum pressure, it would be useful to have a line pressure probe that is able to determine leaks in some other fashion.